Minimal intervention: Advanced lesions

Minimal intervention techniques are generally considered in relation to ini tial carious lesions. However, it appears logical to apply the same princip les to extensive cavities as well as to the replacement of failed existing restorations. As the cavity becomes larger, there is an increasing need to consider protection of remaining cusps because they become seriously weaken ed by loss of the central core of the crown and therefore become subject to the development of splits at the base. However, it is possible to develop a protective cavity design without undue sacrifice of remaining tooth struc ture, at the same time that maintenance of occlusal anatomy and correct con tact with the opposing arch are ensured. For larger cavities, special consi deration needs to be given to the strength of the restorative material. Gla ss ionomer is relatively brittle and should not be exposed to undue occlusa l load. Resin composites cannot be regarded as universal in their physical properties, and placement is time-consuming. A lamination technique is ofte n useful, combining the advantages of both glass ionomer and resin composit e. Amalgam should not be entirely discarded as an option because it has gre ater strength than both glass ionomer and resin composite and is still usef ul for the restoration of extensive cavities and for protection and retenti on of weakened cusps. Minimal intervention principles, designed to limit th e loss of natural tooth structure, should be applied to all restorative den tistry. None of the available restorative materials is entirely satisfactor y in the long term.